“We have seen a united royal family out in force, attending snowy Christmas carols at Westminster Abbey,” he said. “With such displays, they are setting a tone for the new Carolean era and putting behind them the recent turmoil.

“After years of COVID restrictions and concerns, this is a chance for families everywhere to be together and celebrate more freely – although the challenges facing us today, particularly the cost-of-living crisis, are grave in a different way.”

Vickers said the broadcast was a chance for a “quiet message of unity and optimism”, which would be much needed in an increasingly uncertain world.

Averaging between seven and nine minutes, the speech was traditionally written by the Queen herself, with assistance from her husband, Prince Philip, and close aides. It is unclear how much of the blueprint set by his late parents will be retained by the King or whether he is likely to modernise it.

While the theme has not been confirmed, it is likely that Charles will pay tribute to his mother, who died in September. He delivered his first speech as sovereign that month, paying tribute to his “darling mama”, in a remarkably personal broadcast message.

Of his mother, he said: “We owe her the most heartfelt debt any family can owe to their mother; for her love, affection, guidance, understanding and example”.

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The royals and their extended families will gather at Sandringham this year when they will mark a return to the festive seasons of old; the first gathering at the Norfolk estate in three years and the first any of them will have known without the Queen at the helm.

Prince Louis, 4, is expected to take part in the traditional Christmas Day walk to church for the first time, joining his siblings, Prince George, 9, and Princess Charlotte, 7, in scenes that will be broadcast around the world.

Camilla, the Queen Consort, is also expected to invite her children and grandchildren to Sandringham for Christmas for the first time, The Sun reported.

A source told the paper: “Camilla is keen that her family are at the heart of Christmas, particularly as Charles won’t have his youngest son there.”

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